A chain saw includes a motor and a guide bar which includes two guide plates and a spacer plate which is sandwiched between the two guide plates. The guide bar usually is made by metal, and a groove is defined along a periphery of the guide bar so as to receive the chain therein.
A conventional guide bar 60 of a chain saw is shown in FIG. 5 and generally includes two guide plates 62 and a spacer plate 61 which is sandwiched between the two guide plates 62. The spacer plate 61 is shorter than the guide plates 62 so as to form a groove 63 which is defined along the guide bar 60. The chain 70 is connected to the guide bar 60 and movable in the slot 63. When cutting objects, the chain 70 shakes and hits the guide plates 62, and the shocks are transferred to the whole chain saw. Considerable noise is generated due to the vibration of the chain 70 and the guide bar 60.
Another conventional guide bar 80 is disclosed in FIG. 6 and includes two guide plates 82 and a spacer plate 81 which is sandwiched between the two guide plates 82. The spacer plate 81 is shorter than the guide plates 82 so as to form a groove 83 which is defined along the guide bar 80 so as to receive the chain 90 therein. The spacer plate 81 has a first through hole 811, and each of the two guide plates 82 has a second through hole 821 which communicates with the first through hole 811. Vibration can be reduced when it is transferred to the first and second through holes 811, 821 so as to reduce shaking. However, the first and second through holes 811, 821 reduce the strength of the guide bar 80. Besides, when the chain saw cuts a thick object, the object contacts the guide bar 80. Since the guide plates 82 have flat outer surfaces, the friction between the object and the guide bar 80 increases and affects the cuffing efficiency. Once the guide plates 82 are worn out, the whole guide bar has to be replaced.
The present invention provides a guide bar for a chain saws wherein each of the guide plates of the guide bar includes multiple protrusions on the outer side and recesses in the inner side so as to reinforce structural strength of the guide bar and reduces the friction between the guide bar and the object to be cut.